In recent years, a capsule endoscope having an imaging function and a radio communication function appears in a field of endoscope. After being swallowed by a patient, i.e., a subject (human body), from the mouth for an observation (examination), the capsule endoscope travels through inside internal organs (body cavities) such as esophagus, stomach, and small intestine following peristaltic movements and sequentially captures images using the imaging function until naturally discharged from a living body of the patient, in other word, during an observation period.
During the observation period in which the capsule endoscope travels through the internal organs, the capsule endoscope captures images in the body cavities thereby obtaining image data, and sequentially transmits the image data to an outside of the subject body via radio communication, for example, using the radio communication function. The image data received is accumulated in a memory inside an external receiving apparatus. When the patient carries the receiving apparatus equipped with the radio communication function and the memory function, the patient can move freely without inconveniences even after swallowing the capsule endoscope and before discharging the same, i.e., even during the observation period. After the observation finishes, a doctor can display images inside the body cavities on a display unit or the like based on the image data accumulated in the memory of the receiving apparatus, and make diagnosis (see Patent Document 1, for example).    Patent Document 1: Japanese Patent Application Laid-Open No. 2003-19111